>>   The 5000/240 uses the IOASIC SCSI normally, and the problem appears to
>> only be in the TurboChannel-option SCSI that the 5000/200 has.  It's
>> possibl that the problem may show up on the TC-option card on the other
>> systems, but not too many people are using the TC-option card when they
>> have the IOASIC SCSI.  [The IOASIC SCSI will use DMA directly to memory,
>> while all the TC-option SCSI cards have to copy data to/from the on-card
>> memory buffer.]
>
> This machine has 2 additional TC SCSI cards.  So you're saying I should be
> worried?

Single channel SCSI TURBOchannel option card PMAZ-A, the same design
as 5000/200 builtin, runs slower than IOASIC SCSI. 

To me dissappointment, dual channel SCSI TURBOchannel option card
PMAZB-A (TCDS) could not achieve better performance than IOASIC SCSI
of my Personal DECstation builtin.  Probably, the limiting factor is
its artificially lowerd 12.5MHz TC clock rate.  I'm day-dreaming to
have a memory-rich DECstation 5000/260 with the regretful loss of
DECsystem 5900s two years ago... 

Tohru Nishimura
Information Technology Centre
Nara Institute of Science